In PV (photovoltaic) power plants, different parameters are measured, recorded and evaluated at different levels for status monitoring. These parameters include especially the current and power of individual strings, the power of individual zones, which corresponds to the combination of strings, the power of individual inverters, which corresponds to the combination of zones or strings, as well as the power of individual power plant units, which corresponds to the combination of inverters.
The monitoring shows that a high number of erroneous detections can occur, since the cause of the deviation is not always due to the tested component itself. Signal fluctuations from scheduled maintenance, network management, it being overcast and partial light obstructions are some of the significant causes for erroneous detection. Since scheduled maintenance and network management can be solved on an organizational level, they are not further discussed here. Fluctuations caused by overcast skyes can, due to their time dependent behavior, be simply recognized and compensated by evaluating the consistency of the measured signal and averaging. Thus, what is considered are, in particular partial light obstructions.
Partial light obstructions are caused by stationary objects in the vicinity of the PV installation, like buildings, trees, wind rotors or high voltage towers and therefore occur at regular intervals. The partial light obstructions concern the individual elements of the group, like strings or individual modules, but with different intensity at different times.
Recognition of partial light obstructions and especially distinguishing them from incorrect function is complex. A promising approach does not yet exist. Patent applications, patents and other material referred herein are incorporated herein by reference in their entirety.
US 2012/0197557 (EP 2 293 089 A1) discloses a string failure monitoring in which the currents passing through the strings are measured, standardized by means of a reference current and then analyzed. The analysis is standardized over time and occurs at the end of the day.
US 2012/084027 shows monitoring of the power of a PV power plant based on measured data of the strings. Failure and degradation can be better recognized by using monitoring conditions, power limit values and self-calibration.
US 2011/0241720 (EP 0 677 749 A2) discloses recognition of an anomaly in a PV power plant in which the electrical parameters of the strings are measured and mutually compared. Based on the result of comparison a warning unit issues a warning during an anomaly.
Thus, there is a need for improving processing of solar altitude-dependent measured values.
This need and other needs are addressed via the method and features disclosed and/or claimed herein.